Ok, got it I think …
With a role called “test” having the following CSS :
.anvil-role-test .anvil-panel-col {
margin-right: -60px !important;
}
Create a column panel (purely as a container) and apply the role to this.
Drop your labels inside the column panel container and the CSS affects them.
Does that help? I appreciate that might not be the right CSS, but it does at least affect just the required labels.
edit - hmm, Labels with text are displayed slightly differently. Still not right …