Hi @adhamj90,
welcome to the KNIME forum 
Sounds like an interesting use case you are working on!
Do I understand your problem correctly, that you want to predict the next value of the target column based on the last 14 values in the target column and the input features?
If yes, you might want to change the input shape to make use of the sequential factor. If I understand your use case correctly, I think the input shape should be “14, 7”. 14 time steps and for each time step you have a 7 dimensional input for your LSTM.
Does this makes sense?
Having this in mind, you can create training samples for each of your datasets and concatenate the different training samples.
Best
Kathrin
PS: If you want to predict multiple time steps, you can use a recursive loop to use the predicted values to predict the next one.