Apple - Customise Touch Bar for a specific application
Assuming I understand your question, you can set your Touch Bar to show the function keys as its default display on an app by app basis.
To do this:
- Go to Apple > System Preferences
- Select the Keyboard preference pane
- Click on the Shortcuts tab
- In the left sidebar, select the Function Keys option
- On the right-hand side click on the plus + button
- Select the JetBrains PhpStorm app
- Add the app
Now, whenever you are using the JetBrains PhpStorm app, the Touch Bar should display all the function keys.
If you want to REALLY customize your Touch Bar, you'll need BetterTouchTool.
There is a short post on the official BTT site, linking to a long blog post on medium.com illustrating Touch Bar customization using BTT.
In the interest of link rot prevention, here are a couple of Touch Bar screenshots from the blog post.
Holding down Ctrl key for a custom window management bar:
Customized for the PyCharm IDE:
There is a lot more, and the above arrangements were customized by the USER, not the Pycharm developers or even the BTT developer.
Note: I am not affiliated with BetterTouchTool in any way, I just use it and think it's the best quality product of its type—and more people should use it! :)
In addition to Monomeeths answer there's another kind of Touch Bar configuration that is worth mentioning:
System-native way of configuring elements displayed in Touch Bar for specific application is (or at least should be) provided by application itself.
Usually, but not necessarily, this configuration is in View menu. A rule of thumb is to look for Customise Touch Bar... element in one of status bar menus before you start digging deeper in application preferences.
This screenshot is made for Safari browser, however it works the same way for many other applications:
Sometimes applications bury Touch Bar configuration a bit deeper inside their own preferences. For example here's where any JetBrains IDE will have it:
