This add-on will become your best assistant for merging values having same values in adjacent cells (along columns). This add-on will also prove the best ever timesaver, all you need to do is select and click.
Free version restrictions:
* Merge a single set of cells at a time
* Merge all the selected cells in a table range/
Video help: https://youtu.be/h5ylr0CgQ6U
For more details about quotas visit: https://developers.google.com/apps-script/guides/services/quotas