Mastodon 2.8 rolled out recently and it brought some great new features like polls, a follow/followers relationship manager, and featured profile hashtags.
Featured profile hashtags allow you to highlight your favorite topics on your profile. When a visitor taps a featured tag, they’ll see your toots containing the tag (as opposed to most other services which display all public posts with a tag).
To feature hashtags on your Mastodon profile, edit your profile, then click the featured hashtags page. At the top should be some suggestions based on tags you have used. You can click those suggestions to add them to your profile, or manually type in tags.