How can I use [GATE] and [1step] in [IN Sync Mode] in the [CLOCK] settings in the GLOBAL menu?

You can play variety of performances by connecting the SQUID with devices which send audio signals and gate signals (used as trigger signals), you can control play sequence patterns of this unit at a different timing from step playback in sync with master timing clock.
With the [1step] setting, you can use the multi-output of a rhythm machine to advance the steps of the unit to match the sounds of a particular instrument.
With the [GATE] setting, you can play sequence patterns of the unit only a specific period of a sync performance.
For details on trigger signals, see "Synchronizing the unit with an external CLOCK compatible device to play" in the Operating Instructions.
You can download the Operating Instructions from the Pioneer DJ support page
https://www.pioneerdj.com/en/support/documents/production/toraiz-squid/.