When you press the Composer button in the menu, you will see a tree view of a Touchgram.

A new message shows a simple, single page like this.

If you come back to a draft Touchgram after closing the window, you might see a lot more details in the tree.

One icon on the Composer toolbar pops up a page menu. The top two items let you change the Current page and the bottom one adds a page.

The current Detailed Tree composer view doesn't need the page menu so much - it will be more useful when the coming Visual Composer is added. So most of the time you can ignore the Page menu. 

It's faster to tap the Add Page row at the bottom of the list, if that is visible.

This help page was added in case you are wondering why that weird icon and menu are there.

For historical interest, the first version only let you add pages using the Page menu. The simple Add Page row was a user suggestion to improve usability.

On the expander bar there is a little Close button, a circled-x which only appears in the Expanded view.

This is part of the standard iMessage interface so Touchgram cannot do anything about it.

Be very careful about hitting this Close.

The close will cancel the current message you are editing and drop you back into the normal Transcript view of iMessage.

However, Touchgram remembers where you were at. If you were in the middle of editing a message, the draft you'd created is remembered for this conversation. When you go back into Touchgram, what you created will be there for you.

Note: a fun fact from the early development of Touchgram - we weren't going to cope with this until later. None of the other complex iMessage apps did anything smart - they just lost your message if you accidentally tapped the Close button. As the founder's wife was a beta tester, she was rather upset about losing a Touchgram she'd been working on and insisted that version 1 of Touchgram coped with the close. That's why, from the beginning, Touchgram remembers what you're working on.

An iMessage app appears initially in the space normally taken up by the keyboard, at the bottom of the screen. Apple call this the Compact View. 

Some simple apps do all their work in that compact view, like picking stickers. 

Richer apps like drawing apps and  Touchgram use that space as a starting menu and do most of their work in the Expanded View. 

At any time, you can drag that dividing bar or just tap it to switch between views. If you're in the middle of editing a Touchgram, your work is saved. 

Note that saving currently only remembers the details after you have pressed Save in a detail editor. So if you're halfway through designing a sensor for touches and accidentally collapse back to the menu on the Compact view, you will lose that sensor.