I share your frustration. For every feature I publish to AGOL, I have to go in and tweak the order for the symbol types of my feature layer. With a long list of types (in your case, it looks like 20) it is tedious to do this when you create your online map.
To fix this, open your map in AGOL and click the edit button. You will see a list of your symbols for adding a new feature. Below this list of symbols, there is a "Manage" button; click it. To the right of each symbol there will be a small arrow which will allow you to move the symbol up or down in the list. Once the list is in the proper order save the changes, and then resave your map. When you reload the map in Collector, you should see the updated sorting.
As fixing it in this manner is tedious when the list is long, I prefer to use the REST API and edit the JSON file. I have posted some Python code that I use in this post: Feature type sort order in REST API using Python. If you are not familiar with the REST API and editing the JSON file, work with a copy of your feature layer to get familiar with the process.
