How can I change settings in a jpl .css file?

Operating system

Linux

Joplin version

3.5.13

What issue do you have?

I use the embedsearch plugin whose .css file contains a setting for the note's font size, stating

.embed-search-note{
margin-top:-2px;
font-size: 15px;
}
This is too small for me, but I cannot get the font any bigger; nothing I tried so far as managed to override the plugin's built-in setting.

First I edited the .css in the jpl file; changed it to 16px -> no success after restarting Joplin. Then I tried to override the built-in setting with my own userstyle.css, checked the class with the developer tool and added

.embed-search-note {
font-size: 16px !important;
}

No change after restarting Joplin. This was then followed by several other attempts, equally unsuccessful, such as a combination of these 2 commands

div.embed-search {
font-size: 16px !important;
}
.embed-search-note * {
font-size: 16px !important;
}

followed by
#rendered-md .embed-search-note {
font-size: 18px !important;
}

Nothing changed, so what is happening here? I am not a developer; can someone explain what I am missing here; is an override at all possible?

Clueless,
kai.