Help with Google Bookmarks search skills

Using the complex OR is annoying, but being the only workaround I suggest you use it with the combination of the Quick Links Lab feature.

Quick Links by Dan P

Adds a box to the left column that gives you 1-click access to any bookmarkable URL in Gmail. You can use it for saving frequent searches, important individual messages, and more.more.

You will be able to save the complex searches and recall them when needed.

As with most of Google's products, you simply add the same operator again.

In your example, you would use:

label:php label:javascript

If you have a label that is more than one word, use quotes:

label:"label 1" label:"label 2"