Unfortunately, there is currently no direct way to do this. However, you can create an action for this process. Under Window > Actions, set up a new record in the menu. Select the newly created set and in the panel menu, go to New Action – for example, name it "Bleed 3 mm" and click Record:
Then the recording for the action starts and everything you do in Photoshop from now on will be “documented”. The next step is to go to the “Image > Workspace“ menu. There, choose a relative value of 6 mm for the height and width. The reference point should be in the center. This will expand your document by 3 mm bleed all around.
Then you can set up guides along the bleed. To do this, go to the “View > Guides > New Guide Layout” menu and set a margin of 3 mm all around.
After that, stop recording the action. Now from now on you can apply a 3 mm bleed to any document by selecting this action in the Actions panel and pressing the “Play” button.
Post-image: Antoni Shkraba, Pexels