Curated set

Finished pictures and clips, put in the order you want.
Exported at one ratio, numbered.

One of the tools in Aspects for macOS. $19 once, cloud optional.

How it works

One ratio for the set
Every frame leaves at the same aspect ratio, which is what a carousel requires and what it silently crops for you when you get it wrong.
Numbered in the order you set
Zero padded, because an upload picker sorts by name: an unpadded set becomes alphabetical order at the moment of posting.
Stills and clips together
Each comes out in its own medium at the shared size, so a carousel of photographs with one video in it is a single press.
Reorder by dragging
A sequence is the order, so the order is the thing you edit. Cells carry their own files and nothing on disk is renamed when you move one.
Shared treatment
One fit, one background, one set of effects across the whole run, so the set reads as a set rather than as a folder of separate exports.
Output size
Thirteen ratio presets or a custom W by H, with the same six image formats and quality control the other tools use.

Aspects for Mac.
Framing new fresh takes.

Creative tools and proper infrastructure for your work and visual assets.
Your agents rather like it too.

Aspects open on a monitor, editing an image

Creatives, this might actually be all you need.