Javascript: Icons of custom javascripts in toolbar do not display properly

I'm still having trouble with icons of my custom javascripts in the toolbar.

On my 4k monitor (1920 x 1080) the icons look as I intended:

But on my second monitor, 5k (2560 x 1440), the icons are missing:

I rendered the first icon (e.g.) from this PNG via the JavaScript console:

It rendered to:

var strDataToggleCover = "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";

It seems to me, that Acrobat is using different icons for lower or higher resolution of the screen device.

(Until now I can not believe, that I still cannot simply use a base64 encoded PNG for custom icons in the toolbar ...)

Can somebody please give me a hint, what I have to do to make the icons work in any screen resolution?

Thanks,

Tobias