Design: Update the "Run pipeline" form value dropdown to a combobox to accept new values

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

Release notes

Problem to solve

In #29159 (closed) we're making it possible to add a list of values to a pipeline variable so they show up in the "Run pipeline" form. However, such list doesn't allow to add a new value that hasn't been defined.

Proposal

Make it possible to add new values even when a list of values has been defined for the variable. We can use a combobox dropdown input component for that.

Intended users

Feature Usage Metrics

This page may contain information related to upcoming products, features and functionality. It is important to note that the information presented is for informational purposes only, so please do not rely on the information for purchasing or planning purposes. Just like with all projects, the items mentioned on the page are subject to change or delay, and the development, release, and timing of any products, features, or functionality remain at the sole discretion of GitLab Inc.

Edited by 🤖 GitLab Bot 🤖