Crew transfer problem

@Toinkove Yes, command disks.

https://www.simplerockets.com/c/C2M7IC/Small-Space-Station

uses this. There is a command disk between the main habitat and the 'corridor' habitat at the top. Note, the corridor habitat has zero capacity but astronauts can be moved across the corridor, just not into the corridor.

@Darthan184 wait what! You mean the command discs, that have battery and gyro capabilities in them?

A minor addition to this. Crew can also pass across command pods. This is useful in a space station when you have a habitat but no capsule permanently attached.

@Toinkove thanks bro

Actually nvm there's an easier way if this is the "simple Beast" command module.
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just click on its docking port and disconnect the "base" from the "crew tunnel" and reconnect it to the "surface" of the "bruno capsule"

Unless you're referring to the "Simple Beast" that's downloaded with the game, It would help if we could see the craft in question!
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However, I looked at the "simple Beast" Command & Lunar module and it appears there is an issue with it and might also be the case with whatever design you're using.
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in order to facilitate "crew transfer" you must have a "space Habitat" (or one of the space capsules) connected either directly to another "Space habitat" or connected with a pair of docking ports between them. In other words, you can't have any other part (like a "fuel tank") in between a "space habitat" to "space habitat" (or "space habitat" to "docking port") connection!
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in the case of the "Simple Beast" command module, it appears the capsule has a "fuel tank" (that's labeled 'crew tunnel') between it and the docking port. Unfortunately "fuel tanks" will not hold crew members or allow them to pass through! If you did want to make it so a crew could transfer through you would need to remove that part and replace it w/ a "space habitat" section of the same dimensions.