Recently Pick Block ability has been added for touch controls, but unlike the keyboard control, you can use and hold "Control" or "Ctrl" key map to save its content. In touch control however is different, there no such "Ctrl" key for mobile. Block Entity such as chest, command block, structure block, etc does not keep its content/data saved after being Picked.

Touch control steps:

1. Open options in main menu or in world
2. Go to touch
3. Turn on Pick Block(Creative only) toggle
4. Try put some block entity (command block, chest, shulker box, etc.)
5. Put some items in container OR put commands in command block
6. Press Pick Block button

Expected Result(touch)
Block being Picked saves its content. Like PC version

Observed Result(touch):
Block being Picked do not saved its content

Update:
You can actually use pick block to save its content in touch BUT REQUIRED a keyboard input (Bluetooth keyboard)

Touch control step (keyboard input):

1. Insert any data into block (example: write a command inside a command block)
2. Instead pressing the pick block button, you press and hold the "Ctrl" key on the keyboard
3. While holding, press the pick block button on the screen or use the key map

Observed Results (keyboard):
Pick block works normally