You do not need to re-invent exercises in order to get some variation in your training or to change the training emphasis. Sometimes it’s as simple as changing the position of the resistance or the way the load is being held. You could use a barbell or dumbbells. You could use a Goblet hold or hold the weight at your sides. You could do front squats instead of back squats. Simple stuff that leaves you plenty of variations.
With walking lunges you have plenty of variations to play around with just by switching the position of the load being carried. You could carry dumbbells at your side. You could carry a dumbbell in only one arm to challenge your core stability a bit more. You could carry a dumbbell or barbell overhead.
Here I use two different carrying different positions: carrying the kettlebell down at one side and holding another kettlebell overhead in a bottoms ups position to challenge the shoulder and core stabilizers a bit more.