For Multiexcerpt - Cloud: I You cannot add a Multiexcerpt macro or Multiexcerpt Fast Excerpt within a Table cell. The macro gets created outside the table when I you try to insert it into a cell.
This happens only in the new fabric(V2) page editor. It works for the old editor. This is only an issue in Confluence Cloud.
Multiexcerpt Includes CAN be nested in tables, it is only Multexcerpts that cannot.
Atlassian has announced that they will NOT remove the legacy page editor from Confluence so you can use that editor. Rich-text body macros can be nested in Tables in the legacy page editor.
Why it Happens
Atlassian has announced that the new fabric(V2) page editor will not support nested Tables and it will not support rich-text body macros nested in Tables. The Multiexcerpt macros are rich-text body macros.
Nesting of rich-text body macros is supported in Layouts so that may be an option instead of using Tables if you need to use the new fabric (v2) page editor.
Atlassian has announced that they will NOT remove the legacy page editor from Confluence so you can use that editor as a workaround. Rich-text body macros can be nested in Tables in the legacy page editor.Give If your Cloud instances do not have the capability to create "old" pages then contact Atlassian support directly to request that they add that capability to your Cloud instances.
We recommend that you open a support case directly with Atlassian requesting that third party rich-text macros be nestable inside fabric editor Table cells. Please give your feedback to Atlassian about their decision to stop supporting nested rich-text macros by voting on or commenting on CONFCLOUD-58656 and CONFCLOUD-68323.