You can set up a http static folder or create a http endpoint.
Then set the notification node to accept html/javascript. then add a <a href>
html tag with the http static url or endpoint url using msg.payload.file.
e.g. endpoint
[{"id":"03dcc8920c0258d0","type":"ui_ui_control","z":"b9860b4b9de8c8da","name":"","events":"all","x":600,"y":60,"wires":[["166d64eb3d3a96c5"]]},{"id":"166d64eb3d3a96c5","type":"switch","z":"b9860b4b9de8c8da","name":"","property":"name","propertyType":"msg","rules":[{"t":"eq","v":"Home","vt":"str"}],"checkall":"true","repair":false,"outputs":1,"x":730,"y":60,"wires":[["7bebb81c3027c923"]]},{"id":"7bebb81c3027c923","type":"exec","z":"b9860b4b9de8c8da","command":"ls .node-red/static/files","addpay":"","append":"","useSpawn":"false","timer":"","winHide":false,"oldrc":false,"name":"","x":910,"y":60,"wires":[["e0bd7347702a1ee2"],[],[]]},{"id":"af3d9f0f66391b42","type":"file","z":"b9860b4b9de8c8da","name":"","filename":"topic","filenameType":"msg","appendNewline":true,"createDir":false,"overwriteFile":"delete","encoding":"none","x":1230,"y":160,"wires":[["a0f4ec2e59441f0e","7bebb81c3027c923"]]},{"id":"fa000add34d9da3d","type":"switch","z":"b9860b4b9de8c8da","name":"","property":"payload","propertyType":"msg","rules":[{"t":"eq","v":"OK","vt":"str"},{"t":"else"}],"checkall":"true","repair":false,"outputs":2,"x":1110,"y":160,"wires":[["af3d9f0f66391b42"],["7bebb81c3027c923"]]},{"id":"e0bd7347702a1ee2","type":"change","z":"b9860b4b9de8c8da","name":"","rules":[{"t":"set","p":"options","pt":"msg","to":"[$split($.payload, \"\\n\")[$ != \"\"]]","tot":"jsonata"},{"t":"set","p":"payload","pt":"msg","to":".node-red/static/files/","tot":"str"},{"t":"set","p":"topic","pt":"msg","to":"path","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":1120,"y":20,"wires":[["adf4ee957f2bb63a","43036f988b2f6607"]]},{"id":"a0f4ec2e59441f0e","type":"debug","z":"b9860b4b9de8c8da","name":"debug 328","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":1130,"y":220,"wires":[]},{"id":"a04d990df724a403","type":"ui_toast","z":"b9860b4b9de8c8da","position":"dialog","displayTime":"3","highlight":"","sendall":false,"outputs":1,"ok":"OK","cancel":"Cancel","raw":true,"className":"","topic":"","name":"","x":970,"y":160,"wires":[["fa000add34d9da3d"]]},{"id":"adf4ee957f2bb63a","type":"ui_dropdown","z":"b9860b4b9de8c8da","name":"","label":"","tooltip":"","place":"click to delete file","group":"8b5cde76.edd58","order":15,"width":0,"height":0,"passthru":true,"multiple":false,"options":[{"label":"","value":"","type":"str"}],"payload":"","topic":"file","topicType":"str","className":"","x":1140,"y":80,"wires":[["43036f988b2f6607"]]},{"id":"43036f988b2f6607","type":"join","z":"b9860b4b9de8c8da","name":"","mode":"custom","build":"object","property":"payload","propertyType":"msg","key":"topic","joiner":"\\n","joinerType":"str","accumulate":true,"timeout":"","count":"2","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"","reduceFixup":"","x":1290,"y":60,"wires":[["70f36d0d28f26a61"]]},{"id":"364723a1cf2234d5","type":"change","z":"b9860b4b9de8c8da","name":"","rules":[{"t":"set","p":"topic","pt":"msg","to":"$.payload.path & $.payload.file","tot":"jsonata"},{"t":"set","p":"payload","pt":"msg","to":"'confirm deletion<br><br><a href=\"http://192.168.1.10:1880/download/?file=' & $.payload.file & '\" target=\"_blank\"> Download ' & $.payload.file & '</a>'","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":780,"y":160,"wires":[["a04d990df724a403"]]},{"id":"70f36d0d28f26a61","type":"switch","z":"b9860b4b9de8c8da","name":"","property":"topic","propertyType":"msg","rules":[{"t":"eq","v":"file","vt":"str"}],"checkall":"true","repair":false,"outputs":1,"x":630,"y":160,"wires":[["364723a1cf2234d5"]]},{"id":"b5b418eb1329f202","type":"http in","z":"b9860b4b9de8c8da","name":"","url":"/download","method":"get","upload":false,"swaggerDoc":"","x":520,"y":320,"wires":[["eff168b963f64c25"]]},{"id":"eff168b963f64c25","type":"file in","z":"b9860b4b9de8c8da","name":"","filename":"\"/data/data/com.termux/files/home/.node-red/static/files/\" & $.payload.file","filenameType":"jsonata","format":"","chunk":false,"sendError":false,"encoding":"none","allProps":false,"x":680,"y":360,"wires":[["653d1659c9a4fff2","d44a43c3f9ff9fdd"]]},{"id":"d44a43c3f9ff9fdd","type":"function","z":"b9860b4b9de8c8da","name":"function 21","func":"msg.headers = {\n \"Content-Type\": \"text/plain\",\n \"Content-Transfer-Encoding\": \"binary\",\n \"Content-Disposition\": \"attachment; filename=\" + msg.filename,\n \"Content-Length\": msg.payload.count\n} \nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":850,"y":360,"wires":[["d815c952f5a121b8"]]},{"id":"653d1659c9a4fff2","type":"debug","z":"b9860b4b9de8c8da","name":"debug 328","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":830,"y":320,"wires":[]},{"id":"d815c952f5a121b8","type":"http response","z":"b9860b4b9de8c8da","name":"","statusCode":"","headers":{},"x":1010,"y":340,"wires":[]},{"id":"8b5cde76.edd58","type":"ui_group","name":"default","tab":"8f03e639.85956","order":1,"disp":false,"width":"12","collapse":false},{"id":"8f03e639.85956","type":"ui_tab","name":"Home","icon":"dashboard","order":3,"disabled":false,"hidden":false}]
[edit] I forgot to mention that you will need to edit the a href url in the change node prior to the notification node and add your node-red IP.