To make your ex miss you over text, hide your last seen, switch off read receipts, change your profile picture, be cold and non-responsive, ignore them in group chats, etc.
If you want your ex to miss you, hide your activity status. Hiding your last saw won't let them track you, so they'll be curious. Thus, they will always remember and miss you.
Jealousy can lead to wrath, irritation, and resentment, yet a little jealousy between lovers doesn't hurt. Replace your display's couple photo. Put your single photo instead.
WhatsApp sends the sender a blue tick when the recipient reads the message. If you disable read receipt, the sender will not see a blue tick after reading the message. They will go wild wondering if you read their message.
Avoid texting until your head clears or you calm down. If you can't resist, respond briefly. Reply later. Slow down. Consider what to say and how much to convey, then choose your words wisely.
Text message emojis are typically playful. An emoticon can mask rage in a serious communication. Avoid that. Avoid letting them read your emoticons. This may make them think you're moving on and leaving. This may make them reconsider, examine, and respond.
When necessary, speak briefly. Ignore your ex's internet message. Group chats may be responsive. They'll recognize you've moved on and aren't interested.
Give them space and try out new things to make them miss you. Take your time and don't rush the process. Give them space and let them realize the repercussions of your absence.