Insert new cell with indicated actor?

Thanks for such a great tool.

I would like to propose a function.
It would be good if we can insert a new actor (that becomes a new cell) to certain position of table. With this function, I can dynamically add/remove column to make an extendable table UI.

Thanks

No files, tests, or entry points are named. Start by locating the table and cell/actor APIs, then determine how a new actor could be inserted at a chosen position and how columns could be added or removed dynamically; done should include a defined API and verified behavior for those operations.

Written by the indexing model from the issue text.