Whit this Google Form Script you can Automatically Add the “Other:” response from the multiple-choice question or checkbox question to the list of choices for the next user.
There is a plugin for that, but this way you can just paste the script in your Google Form and it will automatically work for you by adding “Other” responses into the list of choices.
So, when a user submits an answer under the “Other:” option from a multiple-choice or checkbox question, that answer is:
- automatically added to the list of choices, and
- it will be automatically available to the next user

How to implement
The implementation is very easy, maybe easier than installing a plugin. So, all you have to do is:
- open the Script editor from the Google Form
- paste the script there
- and just run it once
Here are the detailed instructions:
1. Open the script editor from the three-dot menu on the top right part of the screen.

2. Paste the following script into the editor, first delete everything there.
function firstRun(){
ScriptApp.newTrigger('onFormSubmit')
.forForm(FormApp.getActiveForm())
.