Delete words and history of items searched in Windows Phone Telegram
In Windows Phone, you can delete all searches in the Chat tab by tapping the Search icon and selecting the Clear All option.
Delete words and history of items searched in Android Telegram
But in Android, there is no ability to delete all items at once. You need to tap your finger on the person, group, channel or ID a bit and then tap on the Clear option.
Delete words and history of items searched in Telegram iPhone
On the iPhone, unlike the Android version, you can not delete the search history by tabbing, and you must click on the Clear option.