Losing 'Transparency' is the one problem I encounter with Lightroom Apps, and there seems to be no easy work-arounds.
You can (from Lr v 5.5) [Edit In Photoshop] but your original PNG file opens as TIF (with transparency lost).
You can though (if you do not need transparency) use [Save as a Copy] to save a PNG file from Photoshop.
And with an Action in Ps, you could convert the 'white' background to transparent with the 'Blend if' sliders in Blending Options, if transparency is a 'must have'.
Sorry I cannot be more helpful for your +100 images 😞
Regards. My System: Lr-Classic 12.3 Photoshop 24.5, ACR 15.3.1, Lightroom 6.3.1, Lr-iOS 8.0.8, Bridge 13.0.3, Windows-11.