Button 3 to press modifier buttons only

I am trying to get rid of SteerMouse for this functionality.

CleanShot 2026-01-22 at 09.18.31

I tried creating it here but it seems pressing Button 3 “blocks” the input. If I remove the Button 3 (mouse-up), then it will work after letting go. How can I ignore Button 3’s natural event and bind it to modifier keys like SteerMouse?

I would like it to go Button 3 down => ctrl key down + opt key down, Button 3 up => ctrl key up + opt key up, so basically almost like holding down those keys as long as I hold down Button 3.

Your setup looks good, I just checked and it seems to work fine here.
You could simplify it by using the new action categories:

button3_modifiers.bttpreset (4.9 KB)

Which version of BTT are you running?

Ah but one thing: While Steer Mouse is running / installed, BTT might not work.

Thanks for trying, I’m using version 6.095.

After importing your preset, I see the HUD overlays activating but nothing happening.

If I physically press Ctrl + Option on keyboard it works.

For context, just holding these two keys down and moving my mouse around will resize window from any point using the Rectangle app.

I think maybe Button 3 of my mouse is also sending its own native event that might be blocking it from working? I uninstalled SteerMouse and killed its processes also to be more sure of no conflicts.