When one or more blocks are selected, there should be a UI which presents options to "convert" that block(s) into a pattern which consumes it/them, and preview the selected block in context of the suggested pattern(s).

A rough starting point:

The tricky thing here will be working out which patterns to present... Quoting Matias:

1. We could restrict multi-block transformations to patterns that match exactly the block types of the source. So a paragraph, an image, and a heading would be matched with patterns that have those blocks and nothing else.
2. Transformations could be more loose and expose more patterns, even if it needs to discard some from the original selection. In this case, the transformation would happen on the fly on a best-guess case, assigning blocks to corresponding blocks when it cans, dropping extra ones, and using the pattern to fill in extra blocks.
3. There could be a priority queue for some mappings (i.e if a pattern is made out of two paragraph blocks and the source is a paragraph and a quote, the quote could be transformed into a paragraph since that is an allowed transformation on the Quote block). This can get a bit complicated to reason about and is unclear what tangible value it might bring in the end.