[ustahl]

I have been successfully using the exterior camera, cycling between my U-Boot and other ships, like in SH3/SH4.

Like Sergei pointed out in the other thread, the key is to go into free exterior camera by "F2" first. Once outside your U-Boot you can cycle through, zoom & "ride alongside" the ships in the neighborhood, like in SH3 & SH4 with the keys assigned to "Camera on next unit" and "Camera on prev unit".
I made following (coloured) changes in my Commands.cfg, which gives me above views by pressing "Shift >" and "Shift <".

[Cmd50]
Name=Camera_on_next_unit
Contexts=1,15
Key0=0xBE,s,">"
Page=0x34000000,3714

[Cmd51]
Name=Camera_on_prev_unit
Contexts=1,15
Key0=0xBC,s,"<"
Page=0x34000000,3714

I return to the 1st person view by pressing "F4" (Avatar), which in default Commands.cfg is

[Cmd117]
Name=Avatar
Contexts=1,14,15
Key0=0x73,,"F4"

If you get stuck
Sometimes I get stuck outside the sub and cannot return by simply pressing "F4". One reason for this might be that I went straight into "next unit" forgetting to press "F2" first. To get out of this situation I press "Shift U" (Get Avatar unstuck), which in default Commands.cfg is

[Cmd584]
Name=Get_avatar_unstuck
Contexts=1,14,15
Key0=0x55,s,"Shift+U"

This usually has helped me get back on the bridge and for example switch between Binocular and UZO etc., and continue without problem.