Theory pages in our learning environment often work with expandable blocks, like this one:

You can create one yourself by creating a new Theory page, and then clicking on the Formats button in the toolbar. Choose the option Theory blocks. You can now select an option. What you choose will be written in the blue header in the top-left of a block.

You will see that there is also a block header option. This is used to customize block headers. Select some text and click on the block header option to turn it into the new header. 

Once you have created a block, you can make it expandable by placing your cursor directly under the block. If your cursor is still within the block, simply press Enter and Shift together to move your cursor under the block. This will create a new block under your current block.
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Alternatively, you can go to the source code and exit the block by typing in the new line:

Now, you can create an expansion by clicking on the Formats button in the toolbar above. Choose the option Theory expandable block. You can now select an option. What you choose will be written in the blue header in the button in the bottom-right of a block.

If you place your cursor directly under this block and create a new expandable block, its button will be placed in the main block as well, next to the first one you created. 

It's possible to present information in several ways through tabs in the top-right corner of a block.

To do this, create a block. Place your cursor on the inside of the block and click on the Formats button in the toolbar above. Choose the option Theory tabs. You can now select an option. What you choose will be shown in the top-right of a block.

It's possible to present information in several ways through tabs in the top-right corner of a block.

It will look like this:

Lastly, it is possible to hide content online, but have it show in a (PDF) export. To do so, select text and click on the Formats button in the toolbar above. Choose the option Print only.

Print only looks like this: