A custom block is a reusable piece of content you can place on your site. It's for the rare thing the normal editors don't cover.
You'll find this in the Advanced section. The Advanced section in the left menu starts closed, so click the word Advanced to open it, then look for Custom Blocks.
If you don't see Custom Blocks in the menu, it isn't turned on for your account. Ask the support team and they can turn it on.
Each custom block has a name, a place it appears, its content, and an on/off switch.
Being honest: this is an advanced tool, and most owners never need it. If something feels like it needs a custom block, ask the support team first. There's often a simpler way to get what you want.
Why this matters
Now and then you need something the usual editors don't offer. This is that escape hatch, but a call to support usually gets you there faster.
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