This may come in handy.

Instagram is now experimenting with the feature among some users, allowing you to view how your feed posts will look on your profile grid before posting so you can ensure each update fits into the whole aesthetic of your IG.
some users are seeing a new "Show preview" button within the post composer process. Tap on it and it'll then give you a preview of where the post will fit into your current profile format, including pinned posts.
That would allow you to keep the overall theme and feel of your profile together while making sure that everything you post goes along with the approach you're taking to your main IG presence.

This isn't really game-changing or a big functional change, but it's a really useful update that could really help you decide what to post to IG and when in order to maximize your profile impact. Keeping a consistent approach really, really is key to building your in-app presence, and with that in mind, there could be an awful lot of value in making sure you have the right posts in the right place before publishing.

It is now appearing for all single image, video, and carousel updates, though not yet for your Reels feed for those who have the option available.

We have reached out to IG for an update as to who has it, the scope of the test, and what the plans are for a broader roll-out, and will update this post if/when we hear back.