using schedex indeed works fine.
Here is a first test flow that will create an array, holding the minutes until the next scheduled events are due in ascending order:
[{"id":"11539364.f00b2d","type":"tab","label":"WW Control","disabled":false,"info":""},{"id":"4e2f82c9.62ac8c","type":"schedex","z":"11539364.f00b2d","name":"Mo-Fr am","suspended":false,"lat":"","lon":"","ontime":"05:15","ontopic":"auto","onpayload":"ON","onoffset":0,"onrandomoffset":0,"offtime":"07:00","offtopic":"auto","offpayload":"OFF","offoffset":0,"offrandomoffset":0,"mon":true,"tue":true,"wed":true,"thu":true,"fri":true,"sat":false,"sun":false,"x":300,"y":100,"wires":[["9ecf00b2.2c6ce"]]},{"id":"ea56c399.577b6","type":"schedex","z":"11539364.f00b2d","name":"Mo-Fr pm","suspended":false,"lat":"","lon":"","ontime":"16:00","ontopic":"auto","onpayload":"ON","onoffset":0,"onrandomoffset":0,"offtime":"20:30","offtopic":"auto","offpayload":"OFF","offoffset":0,"offrandomoffset":0,"mon":true,"tue":true,"wed":true,"thu":true,"fri":true,"sat":false,"sun":false,"x":300,"y":180,"wires":[["9ecf00b2.2c6ce"]]},{"id":"6223587.1ffc8a8","type":"debug","z":"11539364.f00b2d","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":1350,"y":520,"wires":[]},{"id":"f728513.8f5dfb","type":"inject","z":"11539364.f00b2d","name":"query","topic":"auto","payload":"info","payloadType":"str","repeat":"60","crontab":"","once":true,"onceDelay":"60","x":90,"y":220,"wires":[["4e2f82c9.62ac8c","ea56c399.577b6","abb14b6a.52b4a8","e6626e84.453cc"]]},{"id":"c3439273.20413","type":"moment","z":"11539364.f00b2d","name":"","topic":"next","input":"payload","inputType":"msg","inTz":"Europe/Berlin","adjAmount":0,"adjType":"days","adjDir":"add","format":"x","locale":"POSIX","output":"payload","outputType":"msg","outTz":"Europe/Berlin","x":870,"y":180,"wires":[["da3d1ecc.4c09f"]]},{"id":"8c2a2b0b.fddc58","type":"switch","z":"11539364.f00b2d","name":"ON Events ","property":"topic","propertyType":"msg","rules":[{"t":"eq","v":"on","vt":"str"}],"checkall":"false","repair":false,"outputs":1,"x":710,"y":180,"wires":[["c3439273.20413"]]},{"id":"9ecf00b2.2c6ce","type":"split","z":"11539364.f00b2d","name":"split Objects","splt":"\\n","spltType":"str","arraySplt":1,"arraySpltType":"len","stream":false,"addname":"topic","x":530,"y":180,"wires":[["8c2a2b0b.fddc58"]]},{"id":"da3d1ecc.4c09f","type":"function","z":"11539364.f00b2d","name":"Minutes-til-next-Event","func":"var Next = msg.payload;\nvar Now = Date.now();\n// msg.topic = \"next\";\nmsg.payload = Math.floor((Next - Now)/1000/60);\nreturn msg;","outputs":1,"noerr":0,"x":840,"y":280,"wires":[["e59df72d.03f858"]]},{"id":"e59df72d.03f858","type":"batch","z":"11539364.f00b2d","name":"Collect Next Events","mode":"interval","count":10,"overlap":0,"interval":"15","allowEmptySequence":false,"topics":[],"x":1090,"y":280,"wires":[["7da40a09.795fd4"]]},{"id":"7da40a09.795fd4","type":"sort","z":"11539364.f00b2d","name":"Sort Next Events","order":"ascending","as_num":true,"target":"","targetType":"seq","msgKey":"","msgKeyType":"elem","seqKey":"payload","seqKeyType":"msg","x":1090,"y":400,"wires":[["cf6b318e.51dc2"]]},{"id":"cf6b318e.51dc2","type":"join","z":"11539364.f00b2d","name":"Array of Next Events","mode":"custom","build":"array","property":"payload","propertyType":"msg","key":"topic","joiner":"\\n","joinerType":"str","accumulate":false,"timeout":"","count":"","reduceRight":false,"reduceExp":"","reduceInit":"","reduceInitType":"num","reduceFixup":"","x":1100,"y":520,"wires":[["6223587.1ffc8a8"]]},{"id":"abb14b6a.52b4a8","type":"schedex","z":"11539364.f00b2d","name":"Sa-So am","suspended":false,"lat":"","lon":"","ontime":"07:30","ontopic":"auto","onpayload":"ON","onoffset":0,"onrandomoffset":0,"offtime":"10:00","offtopic":"auto","offpayload":"OFF","offoffset":0,"offrandomoffset":0,"mon":false,"tue":false,"wed":false,"thu":false,"fri":false,"sat":true,"sun":true,"x":300,"y":260,"wires":[["9ecf00b2.2c6ce"]]},{"id":"e6626e84.453cc","type":"schedex","z":"11539364.f00b2d","name":"Sa-So pm","suspended":false,"lat":"","lon":"","ontime":"18:00","ontopic":"auto","onpayload":"ON","onoffset":0,"onrandomoffset":0,"offtime":"21:00","offtopic":"auto","offpayload":"OFF","offoffset":0,"offrandomoffset":0,"mon":false,"tue":false,"wed":false,"thu":false,"fri":false,"sat":true,"sun":true,"x":300,"y":320,"wires":[["9ecf00b2.2c6ce"]]}]
thanks again for your help!