How to organise Posts within channels

Here are a couple of quick options I can think of:

1:

• Add a consistent hashtag (e.g., #ThemeA, #ThemeB) at the beginning or end of each post.
• Users can then use the search bar in the channel to filter posts by hashtag.

2:

• Create a OneNote notebook or SharePoint page with sections/pages for each theme.
• Link to the relevant section/page in each post.
• Optionally pin the notebook/page in the channel tabs.