Quite surprising that I started the discussion and I am posting the solution 
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Try this out- When you go to the option of adding an app for custom settings in Logitech option+ or in your case any app you use ,it shows you the default list of all the on your PC and down below is the option to browse and select the app. I was encountering the problem when I was selecting the app from the default list but, I tried browse option and selected the app from my desktop shortcut I use to start figma then suddenly all the custom mouse settings for figma starts working.
Try this may be it will work for you also, I hope so
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