It is not possible to manage margin positions using the SaxoInvestor* platform.
You can manage your margin positions in SaxoTraderGO, SaxoTraderPRO or by using the SaxoTrader mobile app.
*Note that SaxoInvestor is currently available in Denmark, Singapore, Australia, Hong Kong, France, The Netherlands, Belgium and the MENA region (UAE, KSA, Bahrain, Kuwait, Qatar, Oman, Lebanon, Jordan, Egypt).