Can't add keyframes to Parameters

[d4rk3lf]

Glad you solved your problem, but I recall having the same (or very similar) issue with 3DS Max few years a go.
It's not related to Tyflow, but it's exactly how you described it.
When you right click, it just deletes the keyframes... or it was deleting selected keyframes on timeline.. something like that...

Can't remember how I solved it... maybe I reinstalled 3DS Max, or reset UI..

Yeah... that was very weird...