How to achieve a "left click and hold" action on trackball

I'm trying to set a button on my Logitech MX Ergo trackball, so when I click and hold for a few seconds it "locks" the left button down till I click again. Windows had that feature, but I cannot get it to work on my Mac unless I use DwellClick. The problem with DwellClick is that if I'm in Photoshop, clicking modifiers for other things, then if I press the keyboard shortcut, it does not work as other modifiers are changing the action... Do I make sense?

I was told that it was prob doable with BTT, so I just installed it, but not seeing where/how to do it.

Any ideas on how to get the click to hold directly on the trackball using BTT?

not exactly what you want, but if you have another button you can dedicate, you can map that button to "Start Mouse Drag" A regular left-click stops the drag.

In theory left-click should work with a modifier should work but I can't figure that out. But I'm brand new to this.