...several years later, I'm interested in this as well!
I saw here that @Andreas_Hegenberg seemed uncertain about being able to preempt macOS's simple, universal 1 Finger Click, if I understand correctly. BTT is nevertheless able to support Corner Click Bottom/Top Left/Right, but on further inspection, it seems that the use of any such gesture then preempts all native macOS clicks in that corner of of the trackpad (even clicks without any modifier keys or other predicates), which obviously can't be extended to preempting all 1 Finger Clicks anywhere on the trackpad...
Another possibility is that Andreas & co. might not want to risk allowing users to shoot themselves in the foot by omitting predicates unwittingly and thus breaking the default 1 Finger Click, or the workload of adding suitable guardrails. But in any case I would love to be able to configure a 1 Finger Click (_with modifiers_) myself.