The third button on the left is "reserved button".
Filters API has a third button for all tabs. Usually, it can be used to open the options menu.
{% hint style="info" %}
The core of the button is `onPress`, the shows of the button depend on whether `onPress` is `null`.
{% endhint %}
Call `FilterBuilder.setReservedButton(ItemGroup, Text, PressAction)` to add the "Reserved button".
```java
FilterBuilder.setReservedButton(CREATIVE_MODE_TAB, new TranslatableText("tooltip.modid.options"), button -> foo());
```
{% hint style="warning" %}
Icon UV is not available in 1.20.6 or above.
{% endhint %}
By default, the icon of the button is the icon that the showcase image above shows. If you want the customized icon, call `FilterBuilder.setReservedButton(ItemGroup, Text, PressAction, Identifier, int, int)`
```java
FilterBuilder.setReservedButton(CREATIVE_MODE_TAB, new TranslatableText("tooltip.modid.options"), button -> foo(), ICONS, 16, 0);
```
## See also
{% embed url="" %}
The javadoc (1.16\~1.19.4)
{% endembed %}
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