In Slack: how can I make the “apply” button available again when pasting Markdown-formatted text?

I often compose Slack messages in a separate text editor (for various reasons not relevant here). Since they’re meant to eventually be pasted into Slack, I use slack-style markdown to stress things or mark code snippets or whatever. And when I paste them, a little pop-up asks if I want to apply the markdown formatting: “Apply” or “Don’t Ask Again”.

The problem is, on one of my machines I must have inadvertently clicked “Don’t Ask Again”, because the popup is gone here. On my other machine I still see it. I feel like I have fully scoured the preferences dialog and can’t find any option to turn the popup back on. How do I reset this? (I’d also accept permanently turning on “apply formatting when pasting”, which would be even more convenient, actually.)

Both machines are running Slack as a desktop application, in Linux (Mint).