If you have a specific idea you want the developers to see, the best places to share them are:

The ASTD Wiki has dedicated sections for user-submitted unit and feature concepts. BEST Beginner Guide For All Star Tower Defense X

If you have 3 or more "Dragon Ball" inspired units, all units gain a 15% Faster Energy Regen.

The ACDX/ASTD Discord is where developers often monitor community feedback and release codes .