Add a custom symbol to palette

Hello,

Iºm using MuseScore 3.4.2 with Linux Mint, and I created this symbol:

swing-8.svg

using this recipe: https://musescore.org/en/node/266325

Everything worked fine except adding the symbol to a palette.
(Iºm using a custom workspace and editing is enabled for the palette)

I can ctrl-shift-drag the image file into a free palette field, but the palette field remains empty.
However, it does function: I can draw the empty palette field to a note, and the symbol will appear. But the palette field always stays empty and does not display its function. In the palette field’s properties, the name is "Image", but not even this word is shown.

Does anyone know how to fix that?

thank you