Excel supports the concept of a PERSONAL.XLS file which contains my personal scripts, which I want to be able to use on any spreadsheet/workbook that I open.
How do
1) You can open your Script and from the Publish menu select "Test as add-on".
2) Now under "Configure New Test" you can select a document and then run the add-on for that doc.
Unfortunately you have to do this for each document one at a time. I would really love it if there was a way to tell a script to be available for all my spreadsheets, or at least have an easy way to install a personal add-on on a per-sheet basis just like you can install an add-on from the marketplace, kinda like a personal marketplace.
Although not recommended, You can also copy set of scripts to all other google spreadsheets programmatically using AppsScriptApi
You cannot do that in Google Spreadsheets. However the best practice is to
However, if you create a copy of a spreadsheet that has an associated script, then the copy will also have the script in it.