If you want to hide a button (actually the group in which the button is configured)…
There is a flow that shows how to play with the UI control node: https://flows.nodered.org/flow/f1b077d49f52866e74e9b983690b470f
Notice that you have to craft carefully the payload to correctly address the tab and group.
Another example below for you to import and test:
[{"id":"80172625.79f6f8","type":"tab","label":"Flow 4","disabled":false,"info":""},{"id":"78e4e0ee.9409a","type":"ui_ui_control","z":"80172625.79f6f8","name":"","x":544.1000518798828,"y":184.0000057220459,"wires":[[]]},{"id":"498029d0.17c038","type":"ui_button","z":"80172625.79f6f8","name":"","group":"2c951b0c.66aa24","order":0,"width":0,"height":0,"passthru":false,"label":"Button group G1","color":"blue","bgcolor":"yellow","icon":"","payload":"","payloadType":"str","topic":"","x":558.1000556945801,"y":126.00000381469727,"wires":[[]]},{"id":"c3848a3b.f4acc8","type":"inject","z":"80172625.79f6f8","name":"Hide G1","topic":"","payload":"{\"group\":{\"hide\":[\"FORUM_G1\"],\"show\":[\"FORUM_G2\"]}}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":314.8888702392578,"y":127.00001335144043,"wires":[["498029d0.17c038","78e4e0ee.9409a"]]},{"id":"31011345.24308c","type":"comment","z":"80172625.79f6f8","name":"Simple example of hiding groups","info":"","x":177.4444580078125,"y":36.11111259460449,"wires":[]},{"id":"6d7781ae.e4927","type":"comment","z":"80172625.79f6f8","name":"https://flows.nodered.org/flow/f1b077d49f52866e74e9b983690b470f","info":"","x":602.77783203125,"y":37.000003814697266,"wires":[]},{"id":"4ba8db51.42ff24","type":"ui_button","z":"80172625.79f6f8","name":"","group":"a47e9d8e.49dbc","order":0,"width":0,"height":0,"passthru":false,"label":"Button group G2","color":"blue","bgcolor":"yellow","icon":"","payload":"","payloadType":"str","topic":"","x":571.0000057220459,"y":262.0000066757202,"wires":[[]]},{"id":"90e0c7b0.50b218","type":"inject","z":"80172625.79f6f8","name":"Hide G2","topic":"","payload":"{\"group\":{\"hide\":[\"FORUM_G2\"],\"show\":[\"FORUM_G1\"]}}","payloadType":"json","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":322,"y":264,"wires":[["4ba8db51.42ff24","78e4e0ee.9409a"]]},{"id":"2c951b0c.66aa24","type":"ui_group","z":"","name":"G1","tab":"70ad3a02.cbf0e4","disp":true,"width":"6","collapse":false},{"id":"a47e9d8e.49dbc","type":"ui_group","z":"","name":"G2","tab":"70ad3a02.cbf0e4","disp":true,"width":"6","collapse":false},{"id":"70ad3a02.cbf0e4","type":"ui_tab","z":"","name":"FORUM","icon":"dashboard"}]