How can I transpose a high dimensional dataset?
This is possible to do in WEKA, but it only works if:


the first column of your data is of string or nominal type, and 
the rest of your columns are numeric. 


Open the dataset in the explorer, and first remove the class attribute by choosing 'No Class' from the drop-down menu on the right. Then, apply the filter from filters.unsupervised.attribute.Transpose. After this, you should re-apply the class attribute by re-selecting the class attribute in the drop-down menu.

If your data doesn't meet the requirements listed above, I would recommend using this short python script to do it:

import pandas as pd
df = pd.read_csv('your_file_here.csv', index=False)
df.transpose().to_csv('your_new_file_here.csv', index=False)


and then loading the new file into WEKA.