The presets are now in groupings such as 'blue gradients' etc but if you don't want that, there is a manual workaround. Display all the panels via the window menu and shapes / gradients etc
To get all the resources in one place (as well as any of your own presets) Go to the right side menu of the presets panels and select legacy as well as the append to have all the 'Photoshop' presets. You can now go to tall the sets and expand
Go to an expanded presets and select all the presets in that set and drag above all the current sets. Repeat this for all the groups of presets
Once you have moved all the presets into a single mass of presets as it would have been with the earlier versions, now go back to the categories and select them all and then goto the right side menu and use the delete groups command and remove them all.
If you want to store them for future use (say you have a corruption of the presets etc) I would suggest selecting all the presets in the panels for the gradients etc and then go to the right side menu and run the export command which will save the presets to a single GRD / ABR etc file.