Issue comes from default width

.control-group .control-label {
    width: 240px;
    padding: .3rem 1rem .3rem 0;
}

Here we could do

.control-group .control-label {
    width: auto;
    padding: .3rem 1rem .3rem 0;
    min-width: 240px;
}

we have to test of any impact.

Also for that peculiar tab, if changed as done above, we dont need 3 columns anymore.
<div class="column-count-md-2 column-count-lg-2">
would fit and we would get

so we have first to see if width auto and mini-width are fine all over admin

Sur Firefox, nous sommes sur de colonnes. Sur Safari trois.

See #28790 (comment) for a possible issue with 2 columns.

not only in 2 columns, but everywhere we have an hr (which is not the case here.

It is an issue under Global Configuration > Banners > Client

ok then. No perfect solution I guess.

Fixed in #30474