How to implement placeholder text which only shows up in composer, not on site?

I’ve written a plugin which pulls a value from postmeta and renders is on a category page. I can drag it from the list of blocks into place, save it, and the plugin behaves as intended. However because the plugin has no content of it’s own, I’m not able to select it in tagDiv composer to make edits.

Does the tagDiv Block API have an option for “placeholder text” or something similar? Or is there a way to output the name of the plugin while in composer? For example, I could do a check in my code to say:

if ($editMode) {
    return 'My block';
} else {
    // do my code
}

• This topic was modified 5 years by technologyadvicecom.
• This topic was modified 5 years by technologyadvicecom.
• This topic was modified 5 years by technologyadvicecom.